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Evaluating environmental conditions that trigger fire-fighting equipment is one of the primary design tasks that have to be taken into account when engineering electrical systems supplying such devices. All of the solutions are aimed at, among others, preserving environmental parameters in a building being on fire for an assumed time and at a level enabling safe evacuation. These parameters include temperature, thermal radiation, visibility range, oxygen concentration, and environmental toxicity. This article presents a new mathematical model for heat exchange between the environment and an electric cable under thermal conditions exceeding permissible values for commonly used non-flammable installation cables. The method of analogy between thermal and electrical systems was adopted for modelling heat flow. Determining how the thermal conductivity of the cable and the thermal capacity of a conductor-insulation system can be applied to calculate the wire temperature depending on the heating time t and distance x from the heat source is discussed. Thermal conductivity and capacity were determined based on experimental tests for halogen-free flame-retardant (HFFR) cables with wire cross-sections of 2.5, 4.0, and 6.0 mm2. The conducted experimental tests enable verifying the results calculated by the mathematical model.

This article presents results of research work aimed at manufacturing photoconductive semiconductor switches (PCSSs) based on semi-insulating (SI) gallium phosphide (GaP) and gallium nitride (GaN). Currently, the work is in progress to determine the optimal values of PCSS parameters. In this article, the parameters of the selected semiconductor materials used for making PCSSs, the device operation principle, and possible areas of use are presented. The paper demonstrates the construction of test PCSSs based on SI GaP and SI GaN and results of blocking characteristics measurements without the illumination, as well as with illumination with a small photon flux. Further research directions are presented also.

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The article presents the experimental results of research works aimed at manufacturing photoconductive semiconductor switches (PCSSs) on semi-insulating (SI) gallium phosphide (GaP) wafers. The PCSS is an electrical switch, triggered into the conduction state by means of an optical pulse with specific photon energy. The switches presented in the paper are developed for the applications in power systems and high-pulse voltage generators. The paper presents time courses of the photocurrent being a response to the excitation of semiconductor material with an optical pulse that generates excess charge carriers. The effects of laser beam photon energy on the height and time constant of photocurrent pulses were determined. The results of measurements of photocurrent in the conduction state for various values of electric field strength are presented. The research methodology was discussed and the measuring system used was described. Possible directions of further research were also presented. The research was carried out thanks to the cooperation of scientific teams from the